Infrasound Tech Silences Wildfires before They Spread
A wildfire burns in the hills of a Los Angeles suburb, jumping from one patch of dry brush to another as it approaches a group of homes. The landscaping of the first house burns, but the house itself stubbornly refuses to catch fire: the small flames that break out along the walls or roof quickly go out. There is no water in sight: the flames are extinguished by sound waves. This type of acoustic fire suppression could soon play a vital role in fighting wildfires.
The key ingredients of a fire are heat, fuel and oxygen; remove one, and the flames go out. Sound waves can smother a fire by drawing oxygen molecules away from the fuel, preventing the fire from getting the air it needs to continue its combustion reaction.
Geoff Bruder, an aerospace engineer who studied thermal energy conversion at NASA, co-founded Sonic Fire Tech to build a sound-generating machine for this purpose. “It’s basically making the oxygen vibrate faster than the fuel can use it, which blocks the chemical reaction,” says Bruder. The company has demonstrated fire suppression up to 25 feet away.
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Using sound waves to fight fire is not a completely new concept. The U.S. Defense Advanced Research Projects Agency studied the method from 2008 to 2011, and university researchers explored the technique over the next decade (including a team at George Mason University that built a subwoofer-like fire extinguisher in 2015).
“The acoustic influence on flames is well known in the field of combustion,” says Albert Simeoni, head of the fire protection engineering department at Worcester Polytechnic Institute in Massachusetts. “The challenge is to evolve the technology without creating disruptive or even damaging sound effects.”
Sonic solves this challenge using infrasound. While previous efforts used sound waves between 30 and 60 hertz, which can be produced with simpler equipment, Sonic stays at or below 20 hertz. These waves are inaudible to humans and travel farther than higher frequency waves.
Homes often catch fire from embers that collect in adjacent foliage or enter attic vents, Bruder says. Sonic’s system uses a piston driven by an electric motor to create sound waves that propagate through metal ducts installed on a building’s roof and under its eaves. The system automatically activates when sensors detect a flame, creating a sort of infrasound force field to extinguish it and prevent re-ignition.
Acoustic waves can have a big effect on a fire, but they only work on small flames, says Arnaud Trouvé, director of the fire protection engineering department at the University of Maryland. Still, homeowners and utilities are willing to try: Sonic is working with two California utilities to demonstrate its technology. The owners have also signed contracts with the company, which aims to have 50 pilot installations by early 2026.
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